1. Field of the Invention
The present invention relates to a developing roller, a process cartridge, and an electrophotographic image forming apparatus.
2. Description of the Related Art
In an electrophotographic image forming apparatus, a developing roller to be used for contact development contacts on a toner amount regulating member which regulates an amount of a toner to be transferred to a fixed value. Therefore, when the surface of the developing roller has strong tackiness, the transferred toner occasionally remains adhering to the developing roller. The toner which has adhered to the surface of the developing roller gradually deteriorates due to the repeated contact of the developing roller onto a photosensitive drum, finally fusion-bonding to the surface of the developing roller, and occasionally causes filming. Japanese Patent Application Laid-Open No. S63-217377 and Japanese Patent Application Laid-Open No. S63-217376 propose a developing roller that reduces the filming by forming a surface layer of the developing roller with a fluorine containing amorphous carbon film having release properties with respect to toner. Furthermore, it is necessary for the developing roller in a contact development system in general to have properties of imparting uniform triboelectric charging to the toner and appropriate triboelectric charging according to the developing process, in order to stably provide a clear and uniform image which has high image density and little printing in a part not to be printed, in other words, so-called little fogging. Japanese Patent Application Laid-Open No. H02-32380 proposes a developing roller that has a surface layer including a SiO2 thin film having high triboelectric charging properties, and imparts a high triboelectric charge to the toner for a long period of time.